[0001] The invention relates to a hydro-mechanical change speed mechanism in particular
for a vehicle adapted to drive associated apparatus whilst travelling at a relatively
reduced speed such as a road sweeping vehicle. 1
[0002] Change speed mechanisms of this kind are useful for road sweeping vehicles or similar
types of machines such as grass cutters or harvesters which need to travel from place
to place at relatively higher road speeds and to be able to creep forward at lower
speeds whilst performing their sweeping, cutting or harvesting functions. This is
achieved by inserting a change speed mechanism into the normal drive train of the
vehicle so that when the mechanism is disengaged normal vehicle operation can take
place using the customary vehicle gear box whilst, for example during sweeping operation,
the change speed mechanism is coupled into the normal drive train so that sweeping
can be carried out in any one of the gears of the normal vehicle drive but with an
additional reduction through the change speed mechanism. In addition at least one
additional drive is taken from the change speed mechanism for driving the associated
sweeping apparatus.
[0003] Suitable change speed mechanisms are of the hydro-mechanical kind and feature a mechanical
gear transmission which drives a vehicle drive pump which can itself be controlled
to control the velocity of the vehicle and which itself drives a hydraulic hydrostatic
motor which is coupled back to the output of the change speed mechanism. The hydrostatic
hydraulic motor can itself likewise be controllable if desired. The overall reduction
of the change speed mechanism thus enables the vehicle to creep forwardly during sweeping
operation. Further pumps for the drive of the associated sweeping apparatus and a
blower can be connected to the change speed mechanism. The blower serves to produce
an air stream which sucks the sweepings from the brooms into the collection tank.
[0004] A mechanical/hydrostatic change speed mechanism of this kind is known for example
from DE-AS 24 55 19 which is also assigned to the assignees in respect to the present
invention. As a change speed mechanism of this kind forms a piece of supplementary
equipment it is important to construct the equipment so that it can be accommodated
on a vehicle chassis with as great an economy of space as is possible.
[0005] The present invention thus starts from a known hydrostatic mechanical change speed
mechanism for a vehicle adapted to drive associated apparatus whilst travelling at
a relatively reduced speed such as a road sweeping vehicle. The mechanism features
an input shaft drivable from the vehicle motor via the normal mechanical vehicle drive,
an output shaft which is adapted to drive the vehicle wheels, either directly or indirectly,
and which is axially aligned with the input shaft there being means actuated by a
driver control selector mechanism for selectively coupling the output shaft to,-or
decoupling the output shaft from, the input shaft. A first gear train comprised only
of gears with axes lying parallel to the input shaft and generally in a plane at right
angles thereto can be connected to the input shaft when the output shaft is decoupled
and is adapted to drive a vehicle drive pump and a drive for the associated apparatus.
A second gear train comprised only of gears with their axes lying parallel to the
axis of the input shaft and generally within a second plane arranged behind and parallel
to the plane of the first gear train is connectable with the output shaft when the
input shaft is decoupled and is driven via a hydraulic hydrostatic motor which is
connected to the vehicle drive pump.
[0006] it is a first principal object of the present invention to provide a hydro-mechanical
change speed mechanism of this kind which is of especially compact construction, .
can be accommodated in a customary vehicle chassis with . great economy of space and
the dimensions of which in the longitudinal direction of the vehicle are as small
as, possible.
[0007] For accomplishing this object the invention envisages that the drive gears of the
first and second gear trains, which . are coupled with the vehicle drive pump and
the hydraulic motor respectively, are displaced to either side of the central longitudinal
plane of the mechanism by a distance sufficient that the vehicle drive pump and the
hydraulic motor can be connected by flanges on the same side of a housing containing
said first and second gear trains. The vehicle drive pump and the hydraulic motor
are preferably connected by flanges on-the input shaft side of said housing.
[0008] As a result of this construction the lower part of the change speed mechanism fits
comfortably between the two side members of a customary truck chassis whilst solely
the upper part of the mechanism which carries the vehicle drive pump and the hydraulic
motor project sideways rather more and are located above the side members of the vehicle
chassis. The arrangement of the vehicle drive pump and of the hydraulic motor on the
same side of the change speed mechanism considerably reduces the dimension of the
change speed mechanism in the longitudinal direction.
[0009] It is particularly advantageous if the flanges for the vehicle drive pump and for
the hydraulic motor are respectively arranged at the same height and at the same distance
from the central longitudinal plane of the mechanism which conveniently coincides
with the central longitudinal plane of the vehicle. This arrangement results in a
uniform utilization of space and makes possible the symmetrical-construction of the
housing halves about the central longitudinal plane as will be later described.
[0010] An especially advantageous embodiment is characterized in that the first gear train
comprises a first transfer gear concentrically and freely rotatably mounted on the
input shaft, means for coupling the transfer gear to said input shaft, a first intermediate
gear meshing with the first transfer gear and supported on a first intermediate shaft
for rotation together therewith and further means for driving the vehicle pump from
the first intermediate genr. In this arrangement the first intermediate shaft is conveniently
located above the input shaft. At the output side of the change speed mechanism there
is conveniently provided a similar arrangement in which the second gear train comprises
a second transfer gear freely rotatably mounted about the output shaft, means for
coupling the second output gear to the output shaft for rotation together therewith,
a second intermediate gear meshing with the second transfer gear and supported on
a second intermediate shaft for rotation together therewith and means for driving
the second intermediate gear from the hydraulic motor. The second intermediate shaft
is preferably axially directly aligned with the first intermediate shaft. In both
arrangements further intermediate gears can be respectively provided on the first
and second intermediate shafts in the drives from the first and second intermediate
gears to the vehicle drive pump and the hydraulic motor respectively.
[0011] In this way the vehicle drive pump and the hydraulic motor can be arranged significantly
higher than and thus above the side members of the vehicle chassis. Above all however,
this embodiment makes it possible for the first intermediate shaft to drive a sweep
or accessory drive pump flanged to the front of the housing. This pump has however
a sufficiently small spatial extent that it can also be arranged in the region of
the side members of the vehicle chassis, i.e. between them on the change speed mechanism.
[0012] It is particularly advantageous if the first gear train comprises in addition to
the drive gear for the vehicle drive pump at least one idler gear meshing with this
drive gear with the idler gear being driven either directly or indirectly in the first
intermediate gear and if the drive gear for the vehicle pump and the idler gear lie
on a line subtending an angle α in the range from 20° to 70° with the central longitudinal
plane. The angle α preferably lies in the range from 30° to 60° and in a particularly
preferred embodiment amounts to substantially 45
0. The second gear train is conveniently laid out in similar fashion and is characterized
in that the means for driving the second intermediate gear from the hydraulic motor
comprises, in addition to the drive gear coupled to the hydraulic motor, a second
idler gear meshing therewith and in that the second idler gear and the drive gear
coupled to the hydraulic motor lie along a line which subtends an angle β in the range
from 20° to 70° with the central longitudinal plane. As before this angle preferably
lies in the range from 30 to 6
0° and in a particularly preferred embodiment is substantially 45
0. It is clearly convenient if the angle α is chosen to equal the angle
[0013] In these embodiments the first and second gear trains branch at the angles α and
β away from the common axis of the first and second intermediate shafts at the above
mentioned preferred angles. This arrangement ensures
; the necessary sideways separation to allow the vehicle drive pump and the hydraulic
motor to be arranged alongside each other. The layout of the first and second gear
trains i.e. the arrangement of gears one above the other in the lower region of the
change speed mechanism and the inclined arrangement in the upper region of the gear
mechanism results in a compact construction which is particularly suitable for mounting
in the vehicle chassis.
[0014] For an exact symmetrical arrangement on both sides of the central longitudinal plane
it is important that the two angles and β are opposed to each other and of the same
magnitude.
[0015] It is useful, for the subsequently to be described identical construction of the-housing
halves and for cost effective manufacture, if, in said first gear train, the drive
gear for the vehicle drive pump and the meshing first idler gear respectively have
the same'divisions as the drive gear coupled with the hydraulic motor and the meshing
second idler gear of the second gear train.
[0016] It is particularly advantageous if the drive gear for the vehicle drive pump also
drives a further pump for auxiliary equipment with the further pump being located
on the opposite side of the drive gear from, and coaxial with, the vehicle drive pump.
The further pump is conveniently flanged to the opposite side of the housing and in
a road sweeping machine is usefully used to drive the blower. The blower drive pump
is thus accommodated without significant constructional trouble or expense and in
a manner very economical of space.
[0017] A further principal object:of the invention is to provide a compact and operationally
reliable mechanism for selectively coupling between the input shaft and the output
shaft, or between the shaft and the drive for the vehicle wheels,-and which is not
sensitive to wear.
[0018] A particularly compact construction in accordance with the invention and which accomplishes
the above-mentioned object is characterized in that the first and second gear trains
include respective first and second transfer gears respectively freely rotatably mounted
on the input and output shafts, with first and second coupling gears respectively
coaxially fixed to the first and second transfer gears for rotation together therewith,
the first and second coupling gears being axially aligned with respective input and
output gears of the same diameter and the same tooth division, said input and output
gears being fixed to the input and output shafts respectively being spaced apart by
a small axial distance and respectively supporting axially displaceable first and
second selector hubs, the first and second selector hubs having matching dogs on their
end faces and the selector mechanism being operative to displace the selector hubs
to respective first end positions, for respectively coupling the input and output
gears with the first and second coupling gears of the associated first and second
transfer gears, and to second end positions in which the matching dogs are engaged
for effecting a drive connection between the input and output shafts.
[0019] The selector mechanism is preferably adapted to jointly displace the first and second
selector hubs to the first end positions and to the second end positions.
[0020] During mechanical drive the input and output shafts are thus rotationally connected
together via the dogs of the first and second selector hubs, in contrast, during hydrostatic
' operation inner toothed rings of the first and second selvetor hubs respectively
rotationally connect the input and output shafts with their respective first and second
Year trains. An advantageous practical embodiment of the Invention is characterized
in that the first and second selector hubs are respectively pivotally connected to
first and second actuating levers with the first and second actuating levers being
pivotally connected to the housing and to one another such that they move necessity
in opposite directions. II one of the actuating levers is now rotationally connected
to an actuating rod located outside of the housing then the change over from hydrostatic
to mechanical drive and reverse can be completed by actuating movement of this single
rod.
[0021] Un abutment ring is advantageously arranged between the input and output gears and
projects radially beyond the gears to form, at its end faces, respective abutments
for the first and second selector hubs The ring however nevertheless allows the end
face dogs of the selector hubs to engage one another. The movement of the selector
hubs towards one another is thus limited by this abutment ring and defines the second
end positions therefor.
[0022] The actuating levers are preferably constructed as selector forks embracing the selector
hubs.
[0023] a further thought underlying the invention is that the change over from mechanical
drive to hydrostatic drive and vice versa should only be able to take place when the
input and output shafts are stationary and indeed without the operator having to pay
particular attention. For this purpose and in accordance with a specially preferred
embodiment of the invention there is provided a releasable stop for fixing the first
and second actuating levers in their positions corresponding to the first and second
end positions the first and second selector hubs. The stop is operative when the input
and output shafts are in rotation but is disengaged when the input and output shafts
are stationary By way of example the stop arrangement can comprise a pump actuated
by the input and output shafts the pressure of which actuates a stop lever so that
change of the change speed mechanism from mechanical to hydraulic drive is not possible.
When the shafts are stationary the pump pressure disappears and the stop is disengaged.
Further constructions of the stop using electric or magnetic means can be conceived
in which no signal is present when the shafts are stationary. so that the stop is
disengaged but in which an electrical voltage is generated when the shafts are rotating
which causes or allows the stop to engage.
[0024] A further principal object of the invention is to provide a change speed mechanism
of the previously named general kind which can be particularly economically produced
by the multiple utilization of the parts that have to be manufactured.
[0025] Thus for this purpose and in accordance with the invention it is envisaged that the
mechanism includes a gear housing containing said first and second gear trains and
that said housing comprises two substantially identical first and second housing halves
which are placed together in opposition along a plane extending at right angles to
the input and output shafts. In this way it is only necessary to manufacture a single
type of housing half for example by casting and subsequent machining in order to produce
a housing for the mechanism of the invention from two such halves. In this way the
storing of spare parts is also simplified.
[0026] It is especially advantageous if the first and second housing halves are each symmetrically
constructed with respect to the central longitudinal plane of the mechanism. The first
and second housing halves should be substantially identically constructed in the vicinity
of the input and output shafts on both sides of the central longitudinal axis. In
the vicinity of the drives for the vehicle drive pump and the hydraulic motor the
two housing halves are however preferably dissimilarly constructed such that the flange
for the vehicle drive pump projects further forwards with respect to the axis of this
pump than the flange for the hydraulic motor. This arrangement is not only useful
in producing a construction which is economical of space but also makes it possible
for the hydraulic connections for the vehicle drive pump and the hydraulic motor to
be axially displaced so that they have room to overlap between these two components.
The axial displacement of the two flanges is also advantageous for the space saving
accommodation of the blower drive pump.
[0027] Whilst the gears in the upper region of the mechanism can easily be journalled on
both sides in the housing because of their sideways displacement this is not possible
for the axially aligned intermediate shafts. In order therefore to make it possible
to support the intermediate shafts at both sides an advantageous embodiment of the
invention envisages that a bearing plate is provided to rotatably support the inner
ends of the first and second intermediate shafts and that this bearing plate is adapted
to be located between the housing halves. The arrangement is conveniently such that
the bearing plate can be introduced into the open side of one of the housing halves
and can be fastened thereto without preventing fitting of the other of the housing
halves. This can for example be achieved by a mirror image arrangement relative to
the central longitudinal axis, and to the transverse axis, of depressions and raised
portions on the housing halves and the bearing plate.
[0028] The invention will now be described in further detail by way of example only and
with reference to the accompanying drawings in which
..are shown:
Fig. 1 a side view of a change speed mechanism in accordance with the invention,
Fig. 2 a plan view of the subject of Fig. 1,
Fig. 3 a front view of the subject of Fig. 1,
Fig. 4 a schematic side view of the inner construction of the mechanism,
Fig. 5 a schematic developed front view of the internal construction of the change
speed mechanism illustrating the arrangement of the two associated gear trails with
the gear trains illustrated displaced sideways by a distance d on either side of the
central longitudinal axis and with the planes of the gear trains folded through 90°,
Fig. 6 a partially sectioned enlarged side view of a section of the change speed mechanism
in the region of the input and output shafts,
Fig. 7 a sectional view on the line VII-VII of Fig. 6,
Fig. 8 a view of a selector hub and of the associated actuating lever as seen in the
axial direction thereof,
Fig. 9 a schematic side view of a sensor for determining whether a shaft turns or
not,
Fig. 10 a view on the line X-X of Fig. 6 to illustrate the manner of operation of
a stop for the actuating lever and
Fig. 11 a plan view of one half of a housing for the mechanism, in particular the
rear half showing the lecative of a bearing plate.
[0029] Turning now to Figs. to 6 there can be seen a hydro-mechanical change speed mechanism
incorporating mechanical gear components and hydrostatic pumps and drives. The change
speed mechanism features a housing 23 which is narrower at its lower region than at
its upper region, where, as can be seen particularly clearly from Fig. 3, it widens
in the manner shown to accommodate flanges '13' and 17' for a vehicle drive pump 13
and a hydraulic hydrostatic motor 17 respectively. An input shaft 11 driven in conventional
fashion from the gear box of the vehicle engine (not shown) enters through a bearing
64 (Fig. 6) from the front into the lower part of the housing 23 and finishes in an
input gear 39 which is fastened to the shaft for rotation together therewith. Directly
opposite to the input gear 39 there is located,at a small distance an identically
constructed output gear 40 at the end of an output shaft 12 which enters the housing
23 from the rear via a bearing 65.
[0030] In a manner not shown but well understood by those skilled in the art, the input
shaft 11 is connected with the output shaft of a normal vehicle gear box whilst the
output shaft 12 is connected to the cardan shaft which leads to the driven wheels
of the vehicle.
[0031] As seen in Figs. 4 and 6 first and second, input and output, transfer gears are supported
on the input shaft 11 and the output shaft 12 respectively. The first and second transfer
gears 24, 32 carry coaxially arranged, first and second coupling gears 37, 38 which
face towards the interior of the mechanism and which have the same diameter and the
same tooth division as the input and output gears 39, 40. The first and second coupling
gears 37, 38 are spaced by only a small distance from the respectively associated
input and output gears 39, 40.
[0032] First and second selector hubs 41, 42 sit respectively one on each of the input and
output gears in order to respectively connect the latter either together or to their
respectively associated first and second transfer gears.via the first and second coupling
gears. For this purpose the selector hubs 41, 42 each carry an inner ring of teeth
44 (Fig. 6) which are able to mesh with the teeth of the input and output gears 39,
40 and with the first and second coupling gears 37, 38. Thus by moving the first and
second selector hubs apart from each other to the position shown in Fig. 6 a drive
can be established between the input gear 39 and the associated first transfer gear
24 and between the second transfer gear 32 and the output gear 40. The first and second
selector hubs 41, 42 are also provided with axially projecting matching dogs or sprags
43 at their facing end faces with cut outs 66 between the individual dogs or sprags.
In this way, by moving the selector hubs 41 and 42 into the position shown in dotted
lines in the lower of Fig. 6, it is possible to directly couple the input gear 39
to the output gear 40 via the dogged connection.
[0033] The opposing end faces of the axially aligned input and output shafts 11 and 12 have
coaxial hollow spaces 67 in which a bearing bar 68 is located which supports the shafts
11 and 12 during rotational movement thereof and in addition supports an abutment
ring 48 arranged between the input and output gears 39, 40. This abutment ring 48
extends radially beyond the input and output gears 39, 4O until approximately the
inner radius of the matching dogs 43.
[0034] The axial extent of the selector hubs 41, 42 is somewhat less than the axial extent
1 (Fig. 6) of the input and output gears 39 and 40.
[0035] Whilst in the lower half of Fig. 6 the first and second selector hubs 41, 42 are
illustrated in their inner end position, in which the dogs 43 of the one selector
hub engage in the cut outs 66 of the other selector hub in order to produce a rotationally
locked connection between the input and output shafts 11 and 12, they are shown in
the upper half of Fig. 6 in their outer end positions in which they connect the input
and output gears 39, 40 with the associated coupling gears 37, 38 via the inner rings
of teeth 44.
[0036] The axial displacement of the selector hubs 41, 42 between the two end positions
takes place as can be seen from Figs. 1, 6 and 8 by respective forked levers or selector
forks 45, 46 which are pivotally journalled at 69, 70 to the housing 23 about axes
which extend at right angles to the direction of movement of the first and second
selector hubs. The first and second selector hubs 41 and 42 are connected to the fork
levers 45, 46 at 71, 72 so that they can rotate relative thereto but leaving a degree
of play in the longitudinal direction of the fork levers. This connection can conveniently
take the form of pegs provided fork levers which engage in annular grooves in the
outer peripheral surface of the coupling rings.
[0037] The actuating fork levers 45, 46 are bent inwardly at right angles at the pivot axes
69, 70 and engage together via a transverse pin 49 on the lever arm 46' and an elongate
slot 50 on the lever arm 45' in such a way that they can only be moved synchronously
in opposite directions and can thus only move the coupling rings 41, 42 synchronously
between opposite end positions.
[0038] The pivot axle 73 of the actuating lever 45 passes out of the housing 23 (as can
be seen in Fig. 8) and is there connected with an actuating rod 47 which is also shown
in broken lines in Fig. 6 and in full lines in Fig. 1.
[0039] In accordance with the invention the input shaft 11 is connected neither with the
output shaft 12 nor with the first transfer gear 24 when the actuating rod 47 is in
its central position which can be seen from Fig. 1. The same applies for the output
shaft 12.
[0040] By moving the actuating rod 47 to the position M of Fig. 1 the change speed mechanism
is switched such that the two selector hubs are brought into engagement as shown in
the lower half of Fig. 6. If the actuating rod 47 is moved ir accordance with Fig.
1 to the position H then the input and putput shafts 11 and 12 are mechanically decoupled,
and the first and second selector hubs are moved to the position shown in the upper
half of Fig. 6 which results in the output shaft 12 being coupled to the input shaft
11 via the hydrostatic drive as will be later explained.
[0041] As can be seen on Figs. 1 to 5 first and second intermediate shafts 25, 31 are arranged
axially aligned one behind the other directly above the input and output shafts 11,
12 and are respectively freely rotatably journalled in the housing 23. The front most
first intermediate shaft 25 carries a first intermediate gear 26 with for example
48 teeth which meshes with the first transfer gear 24 which is freely rotatably arranged
on the input shaft 11 and has for example 56 teeth. A further intermediate gear 27
having for example 49 teeth is also arranged on the first intermediate shaft 25 coaxial
to the first intermediate gear 26.
[0042] As can thus be seen from Figs. 3 and 5 the drive from the first intermediate gear
26 is passed via the shaft 25, the further intermediate gear 27 and an idler gear
29 to a gear 20 arranged to drive the vehicle drive pump 13. The idler gear 29 can
conveniently have 33 teeth which mesh with the 49 teeth of the further intermediate
gear 27 and the 20 teeth of the drive gear 20 for the vehicle drive pump. The idler
gear 29 and the drive gear 20 are arranged one behind the other along a line 28 which
subtends an included angle α of substantially 45° to the central longitudinal plane
22. This arrangement allows the vehicle drive pump 13 with which the drive gear 20
is connected via the shaft 74 to be connected to the housing 23 at the flange 13'
at a position displaced sideways from the central longitudinal plane.
[0043] On rotating the input gear 24 in the clockwise direction the vehicle drive pump 13
is accordingly driven in the counter clockwise direction.
[0044] The gears of the first gear train comprised by the first transfer gear 24, the first
intermediate gear 26, the further intermediate gear 27, the idler gear 29 and the
drive gear 20 is thus constituted only of gears with their axes lying parallel to
the axis of the input shaft and generally within a first plane 18 which lies at the
front end of the change speed mechanism.
[0045] To the right hand side of Fig. 5 there can be seen a second gear train 16 which is
similarly constructed to the first gear train 15 but which can have a different ratio
in the manner illustrated in Fig. 5.
[0046] Thus the second gear train 16 comprises a second transfer wheel 32, having for example
73 teeth which is freely rotataby mounted on the output shaft 12 and which meshes
with a second intermediate gear 34, having for example 31 teethe and which is mounted
on the second intermediate shaft 31 for rotation together therewith. As previously
mentioned the second intermediate shaft 31 is axially aligned with the first intermediate
shaft 25 but is however freely independently rotatable relative thereto. A further
intermediate gear 33 having for example 49 teeth is also rotatably fixed to the second
intermediate shaft 31.
[0047] This further intermediate gear 33 meshes via a second idler gear 36 with the drive
gear 21 which is coupled via the shaft 75 to the hydraulic hydrostatic motor 17 which
is connected via a flange 17' to the housing 23 on the same side as the vehicle drive
pump 13. In similar fashion to the first gear train the drive gear coupled to the
hydrc- static motor 17 and the meshing second idler gear 36 have their axes located
on a line 35 which extends-at an angle β of substantially 45° with the central longitudinal
plane 22. In this manner the mounting flange 17' for the hydraulic motor 17 can conveniently
be placed alongside the vehicle drive pump 13. The vehicle drive pump 13 and the hydraulic
motor 17 are thus attached at the same height and at the same sideways spacing from
the central longitudinal plane 22, to the front side of the housing 23. This arrangement
being made possible by the divergent arrangement of the gear trains represented by
the angles α and β The angles α and should normally lie between 20 and 70°, preferably
between 30° and 60° and the most preferred embodiment as here illustrated should equal
45°. It will be seen from Figs. 4 and 5 that the gears of the second gear train thus
lie generally in a plane 19 parallel to and behind the plane 18 of the gears of the
first gear train and have their axes arranged parallel to one another and to the input
shaft 11.
[0048] As can be seen from Figs. 2 and 4 the drive pump 30 for the blower of the sweeping
machine is flanged to the rear side of the housing 23 and is driven by an extension
of the drive shaft 74 for the vehicle drive pump. The blower drive pump 30 serves
to pressurize a hydraulic (hydrostatic) motor which sets in rotation the suction blower
at the container for callecting-sweepings.
[0049] The second idler gear 36 and the drive gear 21 which is coupled to the hydraulic
motor 17 have 33 and 20 teeth respectively in the same manner as the first idler gear
29 and the drive gear 20 for the vehicle drive pump.
[0050] As can be seen from Fig. 5 the transmission ratio of the first and second gear trains
15 and 16 can be changed in simple manner without changing the position of the individual
pivot axles by simply changing the ratios of the tooth divisions of the individual
gear wheels 32, 34 and 24, 26 respectively.
[0051] Turning now to Figs. 6, 9 and 10 there can be seen an arrangement which allows the
selector lever mechanism(45, 46 for example)to be locked in either of its end positions.
The device features a spring loaded pin 52 which can engage with a projection 51 which
projects in the manner shown in Fig. 6 from the actuating lever 45.
[0052] The pin 52 is connected with an armature 53 of a magnetic coil 54 which is connectable
via terminals 55 to the terminals 56 of a control device 57 (Fig. 9). In the input
circuit of the control device 57 there is located a switch 76 which can be closed
by a pressure actuated piston 77. On closing of the switch 77 the electromagnet 54
is supplied with current and the armature 53 draws the pin 52 out of engagement with
the lever 51 so that the actuating levers 45, 46 can be switched over from one end
position via the intermediate position to-the other end position. A pressure can be
generated in the pressure chamber 78 in front of the piston 77, for example by means
of periodic engagement of a projection 81 on the input shaft 11 and/or the output
shaft 12, which periodically actuates the spring loaded piston 80 which pressurizes
the pressure chambers 78 via . a non-return valve 79. A restrictor 82 ensures that
the pressure in the pressure chambers 78 is maintained at least between each pair
of successive strokes of the piston 80 by the projection 81.
[0053] If the shaft 11 or 12 is stationary then the pressure in the pressure chamber 78
gradually disappears and a spring 83 can push the piston 77 into the pressure chamber
78 so that the switch 76 opens and a spring 84 (Fig. 10) brings the pin 52 into blocking
engagement with the projection 51 on the actuating lever 45.
[0054] The above described blocking arrangement is merely by way of example. It will be
appreciated that the described lock arrangement can be replaced by any other desired-arrangement
featuring devices responsible to the speed of the input and/ or output shaft 12 and
corresponding control devices. It is important that the lock arrangement chosen is
as simple and inexpensive as is possible without sacrifizing reliability. The above
described arrangement has these attributes.
[0055] As can be seen from Figs. 1 to 3 and-11 the housing of the change speed mechanism
is constructed of two identical, first and second housing halves 23a, 23b which are
placed together in opposition, along a plane 58 extending at right angles to the input
and output shafts. Each of the housing halves 23a and 23b is moreover symmetrically
constructed with respect to the central longitudinal plane 22 of the mechanism. In
accordance with the invention the flanges-13', 17' are however so mutually displaced
in the axial direction, i.e. in the direction of the axis of the vehicle drive pump,
that the hydraulic connections 62, 63 of the vehicle drive pump 13 and of the hydraulic
motor 17 are axially mutually displaced in the manner which can be seen from Fig.
2. This arrangement is made possible by the placing of the first and second gear trains
15, 16 in the. spaced apart planes 18, 19.
[0056] In order to be able to rigidly journal the inner ends of the intermediate shafts
25 and 31 on the housing 23 there is provided a specially supported bearing plate
59 which can be seen from Fig. 11. The bearing plate 59 supports the bearings 60 for
the inner ends of the intermediate shafts 25, 31. The bearing plate 59 is accommodated
at its side edges by oppositely disposed mounts 61 and indeed in such a way that after
inserting and fastening the bearing plate 59 for example in one housing half 23b,
the other identically constructed housing half 23a can be positioned without hinderance
in a position rotated through 180 relative to the housing half 23b. For this purpose
vertically displaced projections and cut outs are provided on diametrically opposite
sides of the housing, i.e. to either side of the central longitudinal plane 22. Correspondingly
vertically displaced projections and cut outs of the bearing plate engage with these
cut outs and projections on the housing. The projections and cut outs are arranged
in mirror image symmetry about the central longitudinal axis or plane 22 and are moreover
so arranged that on placing the two housing halves together a projection of the mount
61 in the one housing half lies over a depression in the mount 61' of the other housing
half and vice versa.
[0057] It will be appreciated by those skilled in the art that the afore-mentioned change
speed mechanism can conveniently be located in a vehicle chassis frame with the central
longitudinal plane of the mechanism, i.e. the central plane coincident with the axis
of the shafts 11 and 12, coincident with the central longitudinal axis of the vehicle
chassis.
[0058] It will also be readily understood that the change speed mechanism is also particularly
suited to use in other vehicles such as refuse collection trucks which also need to
creep forward slowly whilst performing an auxiliary function.
1. A hydro-mechanical change speed mechanism in particular for a vehicle adapted to
drive associated apparatus whilst travelling at a relatively reduced speed, such as
a road sweeping vehicle, the mechanism featuring an input shaft 11.drivable from the
vehicle motor via the normal mechanical vehicle drive, an output shaft 12 which is
adapted to drive the vehicle wheels, said output shaft 12 being axially aligned with
said input shaft 11, means 41, 42 actuated by a driver controlled selector mechanism
45,47 for selectively coupling said output shaft 12 to, or decoupling said output
shaft 12 from, said input shaft 11, a first gear train 15 comprise qnly of gears 24,
26, 27, 29, 20 lying parallel to said input shaft and generally in a plane 18 at right
angles to said input shaft, said first gear train being connectable with said input
shaft when the output shaft is decoupled and being adapted to drive a vehicle drive
pump 13 and a drive 14, 30 for the associated apparatus and a second gear train 16
comprised only of gears 32, 34, 33, 36, 11 with their axes lying parallel to the axis
of said input shaft 11 and generally within a second plane 19 arranged behind and
parallel to the plane of the first said gear train 15, said second gear train 16 being
connectable with the output shaft 12 when the input shaft is decoupled and being drivable
via a hydraulic motor 17 which is connected to said vehicle drive pump 13, the mechanism
being characterized in that the drive gears 20, 21 of the first and second gear trains
which'are coupled with the vehicle drive pump 13, 17 and the hydraulic motor respectively
are displaced to either side of the central longitudinal plane 22 of the mechanism
by a distance sufficient that the vehicle drive pump and the hydraulic motor can be
connected by flanges 13', 17' on the same side of a housing 23 containing said first
and second gear trains 15, 16.
2. A hydro-mechanical change speed mechanism in accordance with claim 1 and characterized
in that the vehicle drive pump 13 and the hydraulic motpr 17 are connected by flanges
13', 17' on the input shaft side of said housing 23.
3. A hydro-mechanical change speed mechanism in accordance with either of claims 1
or 2 and characterized in that the flanges 13', 17' for the vehicle drive pump 13
and for the hydraulic motor 17 are respectively arranged at the same height and at
the same distance from said central longitudinal plane 22.
4. A hydro-mechanical change speed mechanism in accordance with any preceding claim
and characterized in that said first gear train 15 comprises a first transfer gear
24 concentrically and freely rotatably mounted on the input shaft 11, means 41 for
coupling said first transfer gear'24 to said input shaft 11, a first intermediate
gear meshing 26 with said first transfer gear 24 and supported on a first intermediate
shaft 25 for rotation together therewith, said first gear train 15 further comprising
means 25,27, 29, 20, 74 for driving the vehicle drive pump 13 from said first intermediate
gear 24.
5. A hydro-mechanical change speed mechanism in accordance with claim 4 and characterized
in that said means for driving the vehicle drive pump 13 from said first intermediate
gear 26 comprises a further intermediate gear 27 fixed to said first intermediate
shaft 25 for rotation together therewith.
6. A hydro-mechanical change speed mechanism in accordance with either of claims 4'
and 5 and characterized in that the first gear train in addition to the drive gear
20 for the vehicle drive pump 13 further comprises at least one idler gear 29 meshing
with this drive gear 20, said idler gear 29 being driven from said first intermediate
gear 26 and in that at least the drive gear 20 for the vehicle pump 13 and the idler
gear 29 lie on a line subtending an angle (α) in the range 20° to 70° with said central
longitudinal plane.
7. A hydro-mechanical change speed mechanism in accordance with claim 6 and characterized
in that said angle (α) lies in the range from 30° to 60°.
8. A hydro-mechanical change speed mechanism in accordance with claim 6 and characterized
in that said angle (α) is substantially 45°.
9. A hydro-mechanical change speed mechanism in accordance with any of the preceding
claims 4 to 8 and characterized in that said first intermediate shaft 25 drives a
drive pump 14 for the associated apparatus said drive pump being connected by a flange
14' to said housing 23.
10. A hydro-mechanical change speed mechanism in accordance with any of the preceding
claims 4 to 9 and characterized in that said second gear train 16 comprises a second
transfer gear 32 freely rotatably mounted about said output shaft 12, means 42 for
coupling said second transfer gear 40 to said output shaft 12 for rotation together
therewith, a second intermediate gear 34 meshing with said second transfer gear 32
and supported on a second intermediate shaft 31 for rotation together therewith and
in that said second gear train 16 further comprises means 75, 21, 36, 33, 31 for driving
said second intermediate gear 34 from said hydraulic motor 17.
11. A hydro-mechanical change speed mechanism in accordance with claim 10 and characterized
in that said means 75, 21, 36, 33,31 for driving said second intermediate gear 34
from said hydraulic motor 17 comprises a further intermediate gear 33 supported on
said second intermediate shaft 31 for rotation together therewith.
12. A hydro-mechanical change speed mechanism in accordance with either of claims
10 and 11 and characterized in that said second intermediate shaft 31 is axially aligned
with said first intermediate shaft 25.
13. A hydro-mechanical change speed mechanism in accordance with any of the preceding
claims 10 to 12 and characterized in that said means 75, 21, 36, 33, 31 for driving
said second intermediate gear from said hydraulic motor comprises, in addition to
the said drive gear 21 coupled to the hydraulic motor 17, a second idler gear 36 meshing
with the drive gear 21 coupled to the hydraulic motor 17 and in that at least said
second idler gear 36 and said drive gear 21 coupled to said hydraulic motor lie along
a line- which subtends an angle (β) in the range from 20° to 70° with said central
longitudinal plane 22.
14. A hydro-mechanical change speed mechanism in accordance with claim 13 and characterized
in that said angle (β) lies in the range from 30° to 60°.
15. A hydro-mechanical change speed mechanism in accordance with claim 13 and characterized
in that said angle (β) is substantially 45°.
16. A hydro-mechanical change speed mechanism in accordance with claim 13 and characterized
in that the angle (β) equals the angle (α) but lies on the opposite side of said central
longitudinal plane 22.
17. A hydro-mechanical change speed mechanism in accordance with claim 13 and characterized
in that, in said first gear train 15, the drive gear 20 for said vehicle drive pump
13 and the meshing idler gear 29 respectively have the same tooth divisions as the
drive gear 21 coupled with said hydraulic motor 17 and the meshing second idler gear
36 of said second gear train 16.
18. A hydro-mechanical.change speed mechanism in accordance with any one of the preceding
claims and characterized in that the drive gear 20 for the vehicle drive pump 13 also
drives a further pump 30 for auxiliary equipment said further pump 30 being flanged
to the opposite side of said housing 23 from, and coaxial with, said vehicle drive
pump 13.
19. A hydro-mechanical change speed mechanism in accordance with any one of the preceding
claims in which said output shaft 12 is adapted to drive said vehicle wheels via intermediate
drive members.
20. A hydro-mechanical change speed mechanism in particular for a vehicle adapted
to drive associated apparatus whilst travelling at a relatively reduced speed, such
as a road sweeping vehicle, the mechanism featuring an input shaft 11 drivable from
the vehicle motor via the normal mechanical vehicle drive, an output shaft 12 which
is adapted to drive the vehicle wheels, said output shaft being axially aligned with
said input shaft 11, means 41, 42 for selectively coupling said output shaft 12 to,
or decoupling said output shaft 12 from said input shaft 11, a first gear train 15
comprised only of gears with axes lying parallel to said input shaft 11 and generally
in a plane 18 at right angles to said input shaft, said first gear train 16 being
connectable with said input shaft 11 when the output shaft 12 is decoupled and being
adapted to drive a vehicle drive pump 13 and a drive 14, 30 for the associated apparatus
and a second gear train 16 comprised only of gears 32, 34, 33, 3f, 21 with their axes
lying parallel to the axis of said input shaft 11 and generally within a second plane
19 arranged behind and parallel to the plane 18 of the first said gear train 15 said
second gear train 16 being connectable with the output shaft 12 when the input shaft
11 is decoupled and being drivable via a hydraulic motor 17 which is connected to
said vehicle drive punp13 in particular in accordance with any one of the preceding
claims and characterized in that said first and second gear trains 15, 16 include
respective first and second transfer gears 24, 32 respectively freely rotatably mounted
on said input and said output shafts 11, 12, there being first and second coupling
gears 37, 38 respectively coaxially fixed to said first and second transfer gears
24, 32 for rotation together therewith, said first and second coupling gears 37, 38
being axially aligned with respective input and output gears 39, 40 of the same diameter
and the same tooth division, with said input and output gears 37, 38 being fixed to
the input and output shafts 11, 12 respectively, being spaced apart by a small axial
distance and respectively supporting axially displaceable first and second selector
hubs 41, 42, the first and second selector hubs 41, 42 having matching dogs 43 on
their end faces, the selector mechanism 45, 47 being operative to displace the selector
hubs 41, 42 to respective fist end positions for respectively coupling the input and
output gears 39, 40 with the first and second coupling gears 37, 38 of the associated
first and second transfer gears 24, 32 and to second end positions in which said matching dogs 43 are engaged for effecting
a driving connection between said input and output shafts 11, 12.
21. A hydro-mechanical change speed mechanise in accordance with claim 20 and characterized
in that said selector mechanism 45, 46, 47 is adapted 45', 46', 49 to jointly displace
said first and second selector hubs 41, 42 to said first end positions and to said
second end positions.
22. A hydro-mechanical change speed mechanism in accordance with claim 21 and characterized
in that the first and second selector hubs 41, 42 are respectively pivotally connected
to first and second actuating levers 45, 46 said first and second actuating levers
45, 46 being pivotally connected to said housing 23 and to one another 45, 46' 49
such that they move of necessity in
directions.
23. A hydro-mechanical change speed mechanism in accordance with any one of the claims
20 to 22 20 to 22 and characterized in that one (45) of said first and second actuating
levers 45, 46 is ronationally connected to an actuating rod 47 outside of the housing.
24. A hydro-mechanical change speed mechanism in accordance with any one of the preceding
claims 20 to 23 and characterized in that an abutment ring 48 is arranged between
said input and output gears 39, 40 and projects radially beyond these gears to form
at its end faces respective abutments for the said first and second selector hubs
41, 42 but however allows the end face dogs 43 of the said selector hubs 41, 42 to
engage one another.
25. A hydro-mechanical change speed mechanism in accordance with any one of the preceding
claims 20 to 24 and characterized in that the actuating levers 45, 46 are constructed
as selector forks embracing the selector hubs 41, 42.
26. A-thydro-mechanical change speed mechanism in accordance with any one of the preceding
claims 20 to 25 and characterized in that a releasable stop 52 is provided for fixing
the first and second actuating levers 45,46 in their positions corresponding to the
said first and second end positions of the first and second selector hubs and that
the stop 52 is operative when the input and output shafts are in rotation but is disengaged
when the input and output shafts are stationary.
27. A hydro-mechanical change speed mechanism in particular for a vehicle adapted
to drive associated apparatus whilst travelling at a relatively reduced speed, such
as a road sweeping vehicle, the mechanism featuring an input shaft 11 drivable from
the vehicle motor via the normal mechanical vehicle drive, an output shaft 12 which
is adapted to drive the vehicle wheels, said output shaft 12 being axially aligned
with said input shaft 11, means actuated by a driver controlled selector mechanism
45, 47 for selectively coupling said output shaft 12 to, or decoupling said output
shaft 12 from said input shaft 11, a first gear train 15 comprised only of gears 24,
26, 27, 29, 20 with axes lying parallel to said input shaft 11 and generally in a
plane 18 at right angles to said input shaft:11, said first gear train 16 being connectable
with said input shaft 11 when the output shaft 12 is decoupled and being adapted to
drive a vehicle drive pump 13 and a drive 14, 30 for the associated apparatus and
a second gear train 16 comprised only of gears 32, 34, 33, 36, 21 with their axes
lying parallel to the axis ofsaid input shaft 11 and generally within a second plane
19 ' arranged behind and parallel to the plane 18 of the first said gear train 15, said
second gear train 16 being connectable with the output shaft 12 when the input shaft
11 is decoupled and being drivable via a hydraulic motor 17 which is connected to
said vehicle drive pump 13 in particular in accordance with any one of the preceding
claims and characterized in that said mechanism includes a gear housing 23 containing
said first and second gear trains 15, 16 and said housing comprises two substantially
identical first and second housing halves 23a, 23b which are placed together in opposition
along a plane extending at right angles to the input and output shafts 11, 12..
28. A hydro-mechanical change speed mechanism in accordance with claim 27 and characterized
in that the said first and second housing halves 23a, 23b are each symmetrically constructed
with respect to tne central longitudinal plane 22 of the mechanism.
29. A hydro-mechanical change speed mechanism in accordance with either of claims
27 and 28 and characterized in that said first and second housing halves 23a, 23b
are of substantially identical construction in the vicinity of the input and output
shafts 11, 12 to either side of the central longitudinal plane 22.
30. A hydro-mechanical change speed mechanism in accordance with either of claims
27 and 29 and characterized in that the first.and second housing halves 23a, 23b are
constructed dissimilarly in the vicinity of the drives for the vehicle drive pump
13 and the hydraulic motor 17 such that the flange 1'3' for the vehicle drive pump
13 projects further forwards with respect to the axis of this pump than the flange
17' for the hydraulic motor 17.
31. A hydro-mechanical change speed mechanism in accordance with any one of the.preceding
claims 27 to 30 and characterized in that said first and second gear trains 15, 16
include respective first and second intermediate gears 26, 34 supported on respective
first and second intermediate shafts 25, 31 for rotation together therewith, said
first and second intermediate shafts 25, 31 being axially aligned with each other,
that a bearing plate 59 is provided to rotatably support the inner ends of said first
and second intermediate shafts 25, 31 and that said bearing plate is adapted 61, 61'
to be located between the housing halves 23a, 23b.
32. A hydro-mechanical change speed mechanism in accordance with claim 31 and characterized
in that said bearing plate 59 is symmetrically constructed relative to the common
rotational axis of said first and second intermediate shafts 11, 12,is mounted on
mounts 61, 61' within the two housing halves 23a, 23b such that the bearing plate
59 can be introduced into the open side of one of the housing halves 23b and can be
fastened thereto without preventing the fitting of the other of said housing halves
23a.